In the course of his confrontation with the Vatican authorities, Galileo Galilei made a flippant comment that nevertheless defined the line between astronomy and religion. He said, “The Bible tells us how to go to Heaven, not how Heaven goes.” Since Galileo’s time, astronomy has frequently clashed with religion over whether God exists. Some consider that the laws of our Universe are improbably finely tuned to allow the creation of life. But if our Universe is just one facet of the multiverse, then there is nothing special about our Universe and there seems no need for God.
Galileo meant by his remark that the Vatican theologians should not attempt to determine the workings of the cosmos by interpreting passages of the Bible. Only astronomy and rational thinking could reveal the way the Universe behaved, he tried to tell them, but this need not detract from the Bible’s role in leading humankind to the salvation of their fragile souls.
When Isaac Newton published his Theory of Universal Gravitation in 1687, he too was attacked on religious grounds, for promoting atheism, because his theory appeared to explain all motion on Earth and in the Universe without the need for God. A religious man himself, Newton stated in response that his theory did not explain gravity, but merely described what it did, and that perhaps God was to be found in the explanation of gravity’s nature. Centuries later, Albert Einstein said that he could not believe in an interventionist deity, that is one that is consciously manipulating reality, but he could believe that the laws of physics were an embodiment of God.
“I believe in [a God] who reveals Himself in the lawful harmony of the world, not in a God who concerns Himself with the fate and the doings of mankind.”
ALBERT EINSTEIN 20TH CENTURY PHYSICIST
These thoughts of great scientists highlight the difference between science and religion: science proceeds from a basis of unambiguous definition that is testable and repeatable, whereas religion is more malleable in its founding principles. In deciding whether there is a god or not, a scientist’s first question would most likely be “What do we mean by God?” In other words, how do we define God?
The Bible talks of miracles, such as the parting of the Red Sea and turning water into wine. Taken literally, these stories strongly suggest that God sits outside the laws of physics. In this case, strictly speaking, no scientific argument can be used to discuss God because He is able to subvert nature to His will: He is supernatural. The argument that today’s scientists would raise against such a supernatural deity is that they see nothing in the Universe that requires such a presence.
Early scientists, however, would talk about investigating nature in order to find God’s place in the Universe. They hoped to uncover phenomena that could not be explained rationally and that therefore required God’s supernatural intervention. As science became more powerful, however, it could explain more. For example, in the 16th century there were those who wondered why the planets move as they do; most thought it was the will of God. Resolving the question was impossible until Tycho Brahe spent his life recording the nightly position of the planets, so that Kepler could derive three laws that encapsulated the apparently disparate planetary motion (see Why Do the Planets Stay in Orbit?). Subsequently, Newton explained that Kepler’s laws of planetary movement were the result of a force called gravity; then in the 20th century, Einstein explained what gravity was and that there must be a fabric of space expanding in all directions (see Was Einstein Right?). Astronomers realized that this implied that the Universe began in a moment of creation, now known as the Big Bang (see How Did the Universe Form?).
The pattern is that, as time goes by, science explains more and more and therefore leaves less and less areas of direct responsibility for a deity. Nevertheless, fundamental questions do still remain unanswered. What triggered the Big Bang? What created life on Earth? Currently these have no explanation, offering space for people to believe in an interventionist god. Many scientists see it differently and simply believe that we have not yet found the full answers. It might be thought that, above all, science is about certainty. Building on the success of Kepler and especially of Newton, scientists of the last few centuries certainly formed the opinion that everything could be predicted: if they could measure the position and the movement of every component in a system, then its future behavior could be calculated precisely. Yet now we know that there is one area of physics in which absolutely certainty is impossible: quantum theory.
Quantum theory deals with probable outcomes (see Are There Alternative Universes?). Although its equations do not allow impossible things to happen, they do allow highly unlikely things to happen. The theory was developed to describe the behavior of subatomic particles, the smallest known things in nature. One of the theory’s architects, German physicist Werner Heisenberg, discovered in 1926 that at the minuscule scale of subatomic particles, the Universe is governed by chance not by certainty. Einstein, however, could not accept that chance played any part in the laws of physics. Without a clear law to predict a particle’s interaction, Einstein thought that there was too much leeway, too much space that could be filled by an interventionist deity. His antipathy to Heisenberg’s idea led to his famous outburst: “God does not play dice!”
The specific idea in Heisenberg’s work that had offended Einstein was that only on the large scale is space a smooth fabric of mass and energy. In the subatomic realm, it is a bubbling mess of particles, which spontaneously form and then disappear in the blink of an eye. Heisenberg found that certain pairs of physical properties, such as time and energy, and position and momentum, were inextricably linked and that the more accurately you measured one, the less accurately you could measure the other. This limit of accuracy has nothing to do with the precision of the equipment used; it is a fundamental uncertainty that is hardwired into the Universe and is known today as “Heisenberg’s Uncertainty Principle.”
“No point is more central than this, that empty space is not empty.”
JOHN WHEELER 20TH CENTURY PHYSICIST
To illustrate the link between the position and momentum of a particle, think of a billiard ball rolling across a table in a pitch black room. To measure its progress, you could roll other balls into the path of the ball and wait for a ricochet. When you hear the balls clip each other, you know that their paths have crossed and so you can say where the original billiard ball is. But in making this detection you have now altered its momentum by knocking it off course and changing its speed. So, although you now know its location, you no longer know its momentum, i.e. where it is going next.
The other pair of interlocked quantities is time and energy. Heisenberg’s leap was to realize that, while energy must be conserved over a certain period of time, over smaller intervals it can be spontaneously created. This has an astounding consequence because it means that pairs of particles, one of matter and another of antimatter, can suddenly leap into existence from nowhere and then quickly annihilate with their partner again. The uncertainty principle sets the time limit for which they can exist. According to the mathematics, the more energy required to make the particle, that is the more mass it contains, the shorter the period of time for which it can exist. As mind-blowing as it may seem, the uncertainty principle does not just apply to particles. Theoretically, anything can be created in such a “quantum fluctuation”—rocks, tables, houses, clouds—nothing in the laws of physics forbids this extraordinary behavior. Even a fully conscious entity could leap into being for a minuscule period of time and, because of the way its brain happened to be “wired” in that moment it could even have the illusion of memories and cognition of the Universe.
As crazy as all of this sounds, astronomers and physicists have good reason for believing in the seemingly far-fetched uncertainty principle because, without it, our Sun would not be shining. The temperature of the solar core, even though estimated to be about 16 million degrees, is too low to force hydrogen nuclei to fuse through collisions. Only when the uncertainty principle is folded into the calculations is nuclear fusion possible: because the positions of the hydrogen nuclei are somewhat uncertain, they can be located anywhere within a small radius of the calculated position and so can approach one another close enough to fuse.
Quantum fluctuations, it seems, are a means of allowing miracles to take place in physics. Other aspects of quantum theory allow particles to behave in even more unexpected ways; certain experimental results can only be understood if the particle involved has somehow been in two places at once. Such discoveries were difficult for scientists to come to terms with; many had been busy trying to explain that the Universe did not need a god at all, that everything could be understood in rational terms. Any highly irrational behavior seemed to strike against that, perhaps even allow a role for God after all. But, for all its weirdness, the quantum uncertainty did not mean that anything could happen. In an infinite Universe something will inevitably happen even if it has only the tiniest of possibility; but—and this is an important “but”—if the chances of something happening are zero, that is it is impossible, then not even an infinite length of time will allow it to happen. So the deduction was that the laws of physics must still be used to distinguish what is possible, however unlikely, from the impossible.
God, on the other hand, should be capable of making anything happen, even if the laws of physics forbid it. Although Einstein never liked the idea of quantum uncertainty, he eventually accepted that it did not necessarily provide a niche for God. In later life he hardened his position still further and rejected the idea of God completely. He wrote in 1954, “The word God is for me nothing more than the expression and product of human weaknesses.”
There has been a strong resurgence in the debate amongst cosmologists about whether there is a role for a divine creator in the Universe. It has sprung from indications that the Universe appears to have been designed specifically for human life. As theoreticians have developed a greater understanding of the laws of physics, so they have been able to investigate what the Universe might have been like had the constants of nature been a little different (see Are There Alternative Universes?). To their surprise, they have found that the vast majority of possible Universes are not hospitable to life. Some scientists call this conclusion the “fine-tuning problem” and believe that it needs an explanation.
As an example of fine tuning, take the rate at which the Universe is expanding. If the expansion rate had been higher than it is today, then matter would have been spread too thinly and the galaxies could not have assembled themselves. At the other end of the scale, if the expansion rate had been too low then the Universe would have collapsed back on itself before stars, planets and humans had time to develop. It is only in a narrow range of values around our current rate of expansion that a Universe with galaxies and stars and planets can form. In general, fine tuning refers to the apparently slim range of values for the physical constants that can give rise to life, and appears to be telling us that the vast majority of possible Universes are sterile, certainly to life as we recognize it. This leads scientists to wonder why a Universe with human life exists at all, given that it is so highly improbable.
“Why does the Universe go to all the bother of existing?”
STEPHEN HAWKING CONTEMPORARY PHYSICIST
Perhaps the best example of fine tuning in the Universe is the so-called “carbon bottleneck.” Carbon is the element that makes the life-giving DNA molecule possible. Like most of the chemical elements, it is built up from simpler atoms in fusion processes inside stars.
In the 1950s, astronomers used everything they knew about atomic nuclei to develop a scenario for the synthesis of carbon, and called it the “triple alpha process.” They envisaged three helium nuclei colliding in sequence to build a single nucleus of carbon. However, the final step of the process was proving difficult to understand. British astronomer Fred Hoyle showed that the reaction rates between beryllium and helium, the two final nuclei to react, were spectacularly mismatched. According to the accepted understanding of nuclear reactions, it should be a very unlikely reaction—so unlikely that carbon should be a rare element in space, and yet everywhere astronomers looked they saw relatively large quantities of it. Unless some way could be found to overcome this carbon bottleneck problem, the formation of the carbon needed for life was inexplicable.
Physics was at an impasse. Hoyle, however, was not—he was bold enough to state the obvious. We see the carbon in the Universe, he reasoned, so it must be produced somehow. What’s more, carbon is an essential part of life on Earth and has resulted in humans with brains capable of deliberating the problem of the element’s formation. So, he concluded, the fact that humans are alive and thinking proves that there is something about the carbon atom that we did not yet understand. He began pondering how nature could speed up the reaction rate between the beryllium and the helium.
Atomic nuclei fuse easily if the two component nuclei have a similar energy state (defined by the internal configuration of the nucleus) to the final product. But, for the known energy states of beryllium and helium, there was no known matching energy state of carbon. Hoyle decided that the fact that he was alive meant that carbon must be capable of holding this quantity of energy, and that all of the experimenters had missed detecting it. The carbon nucleus, he reasoned, would not be able to maintain this energy state for long, otherwise the experimenters would have found it already. So he predicted that although carbon could attain this energy, it must shrug off the excess energy quickly and collapse into the stable form that we see all around us. It need only hold onto the extra energy long enough to make the beryllium-helium reaction possible.
Needless to say, other physicists were highly skeptical, yet when they ran the experiments again, within ten days they had found Hoyle’s predicted energy state for carbon. This was the beginning of so-called anthropic (from the Greek word for man) reasoning, which states that the fact that we are alive should inform our reasoning about what is and is not possible in the Universe. In other words, when searching for the laws of physics we must take into account the fact that these laws must ultimately lead to human beings.
Further investigations in this vein have confirmed that the cosmic abundance of elements is a finely tuned network. Changing the strength of the strong nuclear force, which holds the atomic nucleus together, by just 0.4 percent would destroy this delicate balance and render stars poor factories for carbon. Knowing that life and the Universe is poised on such a knife’s edge makes us continue to wonder: why should the formation of the elements be so finely balanced as to make life on Earth possible?
“The Universe we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good.”
RICHARD DAWKINS CONTEMPORARY BIOLOGIST
The short answer to the question of our improbable existence is that no one knows. Some believe the question to be nonsensical because if the Universe had not been like it is, we would not be here to ask the question. Others believe that there must be a profound reason: God made the Universe this way by designing the laws of physics specifically to allow human beings to exist. This would certainly conform to Einstein’s noninterventionist God but has an uneasy resonance with the mindset of early 19th century naturalists.
By the early 1800s, human investigation had revealed the most amazing fit between the various life forms and their environments. It was thought to be clear proof that God had designed the world to be perfectly suited for the life it contained. But in 1859, Darwin turned this thinking on its head by presenting his observations that life forms can change with each successive generation to adapt to their surroundings. This idea of natural selection led to the theory of evolution and the belief that the planet and its environment are largely accidental and that life forms evolve by random trial and error—mostly error—to fit whatever niches are available. According to Darwin, the ability to evolve is hardwired into organisms because of an error-prone copying mechanism in the cellular machinery. While some conservative Christian groups continue to believe in “Intelligent Design,” the consensus in the scientific community is that what was once thought of as evidence of the perfection of God is actually imperfect engineering on the molecular level.
So, could the same be true of the Universe at large—that the fine tuning we see around us is the result of some form of cosmic evolution? This is where the multiverse comes in; if the M-theory landscape is correct (see Are There Alternative Universes?), then every possible universe with every possible combination of physical constants is tried out, because there is an infinite number of universes. Inevitably there will be at least one where human life is possible, however finely tuned we need the laws of physics to be. With this view, there is nothing special about our Universe: we just happen to have evolved in the one best suited to the development of our life form; and so there is no cosmological need for God.
“The impression of design is overwhelming.”
PAUL DAVIES CONTEMPORARY COSMOLOGIST
There is a caveat to keep in mind when discussing fine tuning and its possible implications—do we perceive that our Universe is fine-tuned for the development of life simply because we lack the imagination to envisage other possibilities? The Universe constantly takes us by surprise, presenting us with wonders that we have neither the wit nor the experience to anticipate. An excellent case in point is the detection of planets around other stars. Astronomers had assumed that the distribution of planets would follow the familiar one of our Solar System: rocky planets close to the Sun and gas giants further out. One team was even collecting data but not analyzing it because they were certain that they would need a decade of observations in order to see Jupiter-like planets in their long orbits. In fact, the first detected planets were indeed Jupiter-sized, but orbiting closer to their star than any planet orbits the Sun. The discovery took astronomers completely by surprise, revealing something that they had thought impossible. Could it be that other, previously unthought-of, or discounted, routes to life would be available with other constants of nature? Until we can define what life is (see Are We Made From Stardust?), and thus have a concrete rule for what is and is not alive, the discussion of whether we live in a finely tuned Universe is perhaps premature.
“The treasures hidden in the Heavens are so rich that the human mind shall never be lacking in fresh nourishment.”
JOHANNES KEPLER 17TH CENTURY ASTRONOMER
Much that we can see and study remains unexplained. The closer we look at the Universe, certainly the more we understand; yet, at the same time, the more mysteries and the more wonder we uncover. Perhaps this will be the pattern of physics forever and there will never be a theory of everything, just an infinite succession of finer and finer details. Or perhaps the final all-embracing theory is just around the corner. Either way, we can be fascinated by cosmology for the journey of discovery that it epitomizes, as well as for the ultimate answers to the big questions that it may deliver.